1. Field of the Invention
The present invention relates to a plate link chain, particularly for a motor vehicle drive system, with a large number of link plates hingedly connected to each other by rocker members, where the rocker members extend transversely to the longitudinal direction of the plate link chain. Located on each of the rocker members and link plates there are curved contact surfaces, along which the rocker members and link plates are in contact with each other to transmit power. Also located on the rocker members are curved pitch surfaces along which the rocker members roll against each other to transmit power.
2. Description of the Related Art
Such a plate link chain can be a toothed chain, which can be employed, for example, to transfer power in an all-wheel power divider transmission of a motor vehicle, or also, for example, on an auxiliary unit of the internal combustion engine of the motor vehicle. In the named cases the plate link chain is designed as a toothed chain and transmits tractive force between a driven and a driving sprocket wheel. Such a plate link chain can also be used, for example, as a traction medium in a belt-driven conical-pulley transmission of a motor vehicle, where, in this case, the tractive force is not transmitted by a positive connection through a toothed engagement of the plate link chain with the sprocket wheel, but by frictional force between two conical pulley pairs of the belt-driven conical-pulley transmission.
Such a plate link chain installed in a belt-driven conical-pulley transmission is also referred to as a rocker joint chain, where the rocker members or pressure pieces are arranged in pairs in plate openings of the link plates, and have pitch surfaces that roll against each other. In doing so they absorb the tractive force transmitted by the plate link chain in the form of compressive stresses, and introduce corresponding forces into the link plates as the reactive force thereto, where the transfer of force between the rocker members and the link plates takes place at curved contact surfaces that are formed on the rocker members and the link plates.
Thus, such a plate link chain has an articulating function, which is taken over by the rocker members with their respective pitch surfaces, and a contact function between the rocker members and the link plates, and for this purpose they must be designed in accordance with the required strength. If a deflection of the plate link chain from its stretched position occurs, when the chain changes from its stretched position to a deflected position—for example when the plate link chain runs over sprocket wheels or is clamped between two conical pulleys and bends—there must be high security against rotation between the rocker members and the link plates, since otherwise relative motion between the link plates and the rocker members results in friction-induced wear and hence in a possible early failure of the plate link chain.
The transmission of force between the rocker members and the link plates usually takes place in the area of a contact surface between the link plates and the rocker members, which, regarded along the longitudinal direction of the plate link chain, is located opposite the pitch surfaces of the rocker members, i.e., in the area of the back surfaces of the rocker members. At this contact surface between the rocker member and the link plate, the rocker member introduces a compressive force into the link plate which, due to the spacing present between the place where the force is introduced into the link plate and the upper or lower edge area of the rocker member receiving opening of the link plate, viewed in the direction of the rocker member height, results in a moment which promotes the formation of cracks in the link plate, and as time goes on can lead to growth of the cracks and thus to failure of the link plate.
A link plate is known in which there is not only one contact surface present between the rocker member and the link plate—namely the rear contact surface, relative to the pitch surfaces between the rocker members, viewed in the running direction of the plate link chain, which is formed on the rear surface of the rocker member. But two contact surfaces are formed between the rocker member and the link plate, one of which is located above and one below a plane that bisects the rocker member across the height direction, viewed transversely to the longitudinal direction of the plate link chain. This design has the advantage of division of force over the design with only one contact surface.
Based on U.S. Pat. No. 4,507,106, a plate link chain for the transmission of force is known in which the rocker members have pitch surfaces opposite each other and there are two contact surfaces formed on the rocker members at which the rocker members are in contact with contact surfaces of the link plates, and which serve to transmit power. The rocker members of this plate link chain, regarded in a cross sectional view running transversely to the longitudinal direction of the plate link chain, have a nearly circular shape in the area of the contact surfaces, and hence have the disadvantage of inadequate protection against rotation, so that relative motion can occur between the rocker members and the link plate when the chain is deflected, which leads to significant wear in the contact surface area between the rocker members and the link plates, and hence to early failure.
An attempt was made to solve this problem of safeguarding the rocker members against rotation of the link plates with the plate link chain known from U.S. Pat. No. 4,010,656 by having the contact surface area of the rocker members and the matching contact surface area of the link plates are not almost circular in shape—since such a design promotes relative rotation of the rocker members in the link plates—but by having the rocker members nearly triangular in shape in a corresponding cross sectional view, so that largely straight-lined contact surfaces on the rocker members are in contact with largely straight-lined contact surfaces of the link plates, so that safeguarding against rotation was realized. If this known plate link chain transitions from an extended position to a curved position, such a design may work against rotation of the rocker members in the link plates, but the rocker members are supported on their edges on the link plates. Such edge supporting results in significant tension peaks in the area of the contact surfaces between the rocker members and the link plates, so that such a design again also promotes the growth of cracks on the link plates, and the life of the known plate link chain is thereby reduced.
Starting from this point, an object of the present invention is to provide a plate link chain, in particular for a motor vehicle drive system, with which lower loads on the link plates are realizable, while the cross sectional area of the rocker members remains largely the same in comparison to known plate link chains, and provision is also made for the requirements for anti-rotation protection of the rocker members in the link plates.